In recent years, from the viewpoint of preventing the destruction of the ozone layer, refrigerants enclosed in refrigeration cycle apparatuses that cool objects using refrigerant circulations (refrigeration cycles) have shifted from traditional refrigerants to chlorine-free refrigerants. Because chlorine-free HFC refrigerants (e.g., R410A, R404A) have relatively high warming potential, measures are taken to prevent leakage of the refrigerants to outside the refrigeration apparatuses, and it is mandatory to collect the refrigerants at the time of disposal of the apparatuses. However, because the collection rate may be insufficient and the refrigerants may leak when in use, a further shift to refrigerants with small global warming potential (GWP) values has been demanded. Examples of such refrigerants with small GWP values under study include natural refrigerants, such as carbon dioxide, and HFO (olefinic fluorine compound)-based refrigerants (hereinafter referred to as HFO refrigerants), such as HFO-1234yf (hydrofluoroolefin) and HFO-1234ze (tetrafluoropropen).
One example of a traditional refrigeration apparatus that uses an HFO refrigerant is an apparatus that includes an ejector and a gas-liquid separator (see, for example, Patent Literature 1). In this apparatus, a gas refrigerant separated in the gas-liquid separator is returned to a compressor, and a liquid refrigerant separated in the gas-liquid separator is made to evaporate in an evaporator and then sucked into the ejector.